1. Field of the Invention
The present invention relates to a method for providing a lamination film with adhesive, a method for applying hot melt to a lamination film, the application for such a method, a plant for laminating a carrier member with a lamination film, as well as a method for upgrading a plant.
In particular, the invention relates to a method for laminating components with film, whereby an adhesive is so applied in grid pattern to the surface of the lamination film and/or the component, and that, after assembling the film and the component, the adhesive is arranged between the film and the component, and a channel system formed between the areas of applied adhesive to enable the uniform removal of the air lying between the component and the film (removal of the air by extraction and/or pressing out).
Furthermore, the invention relates to a laminated mold part that is obtained through the above-mentioned method, as well as the use of an adhesive grid pattern that is arranged between a component and a lamination film in order to reduce or avoid entrapping air during lamination of the component with the lamination film.
2. Description of the Related Art
The lamination of components by applying a negative pressure or vacuum, such as vacuum lamination or variants such as the in-mold graining (IMG) process and/or by means of pressing power, is widely used in industry.
In vacuum-assisted lamination methods, generally an airtight or partially air-permeable material (e.g. a decorative film) is laminated on a solid component. The adhesive used can be applied as a pre-coating on the film or the component.
In this process, the film can be heated and then applied to the component by applying a negative pressure. The heat energy required for the film forming can also be used for activation of the adhesive. A distinctive condition for the process is the air permeability (vacuum capability) of the substrate (component) to be laminated in combination with an airtight film. The latter can be achieved for example through an additional membrane.
While the vacuum capability is usually obtained by the use of porous materials such as wood-based materials or open-pore composite materials, in the case of airtight component materials, such as are typically produced by injection molding or partially air permeable component materials, such as, for example, in the case of fiber composites, special precautions need to be taken. These usually include the introduction of vacuum holes and the application of a lamination graining on the component, which allows extraction of the air contained between the film and component. The lamination graining gives rise to grain channels in the component through which the air located between the component and the film can be extracted.
The vacuum holes permit the extraction of the air between the film and the component by applying a negative pressure or vacuum. However, this is often not sufficient to avoid small to medium sized air pockets occurring. This may be caused, for example, by the geometry of the components, but also by the deposition process of the film and the limited capacity of the vacuum holes. Therefore, in the prior art, lamination graining is usually also applied to the component, which also allows further air extraction through the channels of the grain to the holes following the “first contact” of the film with the component. However, the application of this lamination graining to the component is technically complex and costly, especially since a sufficient grain typically requires a depth of 0.2 to 0.3 mm, which leads to a correspondingly higher use of material and also increases the overall weight of the component. This can represent up to 10 wt.-% of the component weight.
In the automotive sector, particularly for components in the interior of vehicles, i.e. typically two different processes are used in practice for the film lamination in the preferred application.
In a first method, the adhesive is applied by spraying it onto the component. In this case, a varnish-like adhesive application must be avoided as this can lead to the clogging of the vacuum holes by the adhesive (e.g. when using a dispersion or solvent adhesive).
In an alternative method, the adhesive is applied to the film (e.g. a hot melt substance). In this case, the hot melt adhesive is heated and activated with the film up to the typical required film deforming temperature (depending on the film: 120° C. to 210° C.).
In the latter process, the adhesive is a viscous liquid (usually a reactive or thermoplastic melt adhesive). This is the case even in the vacuum joining process. The viscous adhesive can easily clog the vacuum holes or grain channels because of its fluidity. This prevents the uniform extraction of the air and can thus favour the formation of air pockets. This results in visible but also invisible defects in the finished laminated molding.
In fact, the expert is aware that these kinds of defects caused by air pockets, often occur when using hot melt adhesives; the demands on grain quality, and the requirements with respect to the quality and depth of the grain as well as the number of holes are higher than in the case of the first-mentioned process, where the adhesive is sprayed on the component.